1. Field of the Invention
The present invention relates to a laser projection system, and more particularly, to an alignment laser projection system which can accurately align; working lines without being affected by interference that can occur internally during the working process of a machine tool.
2. Description of the Related Art
In order to construct an external ship body or an internal structure in a large structure such as a ship, a very wide steel plate is needed, but it is impossible in reality to produce such a wide steel plate. Accordingly, for that purpose, a plurality of steel plates of a predetermined area are joined by welding and then used.
Meanwhile, if the welding parts of steel plates are not accurately joined in a predetermined allowable error range, the strength of a predetermined part of a ship body produced based on the welding can be relatively weaker than other parts and due to this, the ship body may be broken. Accordingly, the welding between joining steel plates should be performed after an accurate welding line is formed.
However, the area of each steel plate joined by welding is also much wider than an ordinary area of a steel plate such that it is difficult to apply normal welding line forming methods, such as those using worker's eye measure or a measuring tape. Accordingly, in this case, a laser projection system shown in FIGS. 1 and 2 is used for the alignment.
Generally, a laser projection system 1 comprises a housing 40 internally which has a laser irradiation unit, a driving unit container 50 which is coupled to one side of the housing 40 and internally has a driving unit 52, an encoder container 60 which is coupled to the other side of the housing 40 and internally has an encoder 62, a control unit 70 which is connected to the driving unit 52 and the encoder 62 and controls the driving unit 52, and a display 80 which displays the situation controlled by the control unit 70.
Inside the housing 40, disposed are a ball screw 20 which can be extended or contracted in the direction from the center to either side with being held through penetration holes (not shown) formed on both sides of the housing 40, a first irradiation unit 32 which is fixed to the center of the ball screw 20, and at least one pair or more of second irradiation units 34 and 36 which are coupled to the ball screw 20 at symmetrical locations about the first irradiation unit 32. Cables 33, 35, and 37 are connected to the first and second irradiation units 32, 34 and 36, respectively.
As the first and second irradiation units 32, 34, and 36, normal laser units are used respectively.
The cables 33, 35, and 37 provide power from a power supply unit to the first and second irradiation units 32, 34, and 36, respectively. In addition, the first and second irradiation units 32, 34, and 36 transmit information on respective moving distances to the control unit 70.
The driving unit 52 is connected to one end of the ball screw 20 to extend or contract the ball screw and for this a stepping motor is usually employed.
The encoder 60 is connected to the other end of the ball screw 20, and if the ball screw 20 is extended or contracted by the driving unit 52, transmits information on this moving distance to the control unit 70.
The control unit 70 controls start and end of operation of the driving unit 50, and the driving range, receives information on the moving distance of the ball screw 20 measured by the encoder 60, and displays the control situation for these on the display 80. An ordinary terminal or CPU with a control function corresponds to this unit 70.
The display 80 displays the situation controlled by the control unit 70. An ordinary monitor corresponds to this, and of course, a touch screen can also, be used.
In the operation of the laser projection system having the structure described above, first, objects desired to be welded (A, B, C, D) are placed below or beside the laser projection system. Then, from the external power supply unit (not shown) through the respective cables 33, 35, and 37, power is supplied to the first and second irradiation units 32, 34, and 36 connected to the, respective cables 33, 35, 37.
If power is supplied, light beams irradiated by the first and second irradiation units 32, 34, and 36 accurately indicate straight welding lines between the objects to be welded (A, B, C, D), and according to this, a worker performs welding work using a welder 90 and so on.
Meanwhile, in order to form an accurate welding line, if the driving unit 52 is driven, the ball screw 20 connected to the driving unit 52 is extended or contracted from the first irradiation unit 32 to the right-hand side or left-hand side. According to this, a pair of the second irradiation units 34 and 36 coupled to the ball screw 20 move to the right or to the left such that an accurate welding line can be adjusted and along thus aligned welding line, the welder welds the objects and then the desired structure can be produced.
However, when the prior art laser projection system with the structure described above are frequently used in welding fields, the ball screw 20 is extended or contracted particularly by the driving unit 52, and according to this, the cables 35 and 37 connected to the second irradiation units 34 and 36 among the first and second irradiation units 32, 34, and 36, which move together with the ball screw 20, frequently contacts with an inner wall surface of the housing 40 such that the cables 36 and 37 are frequently damaged.
These damages of the cables cause error in the location information of the irradiation units transmitted to the control unit through the cables such that it becomes impossible to align an accurate welding line originally desired and when the welding work is completed, this can directly cause serious damages to the finished structure.
In addition, it causes difficulties in providing power to respective irradiation units from the external power supply unit or a laser beam desired to irradiate itself is not generated. Accordingly, the laser projection system should be regularly inspected and frequently replaced and this becomes one of major factors for deterioration of the entire productivity.
This problem also occurs identically in all cases where a laser projection system with the identical structure is needed for more accurate position alignment, such as when the laser projection system is used for position alignment in manufacturing tires, and when an iron plate is manufactured in a predetermined shape after a blast furnace process.